The GKit “Baby Pre” is a two-channel microphone preamplifier kit designed to help teach the basic concepts of electronics relevant to students of audio. It is intended for use in university level audio programs to help teach students about voltage, current, impedance, analog signal transmission, gain, filtering, trouble-shooting and more.There is no complicated harness wiring or metal work required and an individual with little to no soldering experience can complete the kit in approximately six hours.

 

Each of the two channels has a gain control as well as push-buttons for +48V phantom power, a high-pass filter, pad, and a class-A “color” stage. The inputs and outputs are on balanced XLR connectors, and the power supply uses an external “wall wart” AC transformer to ensure there are no potentially hazardous voltages during assembly and testing. The Baby Pre is a low-cost kit with full documentation available. The GKit baby pre will surprise you with its quality and versatility in such a small package.

“Baby Pre” Included Concepts:

1. Ohm’s Law: Familiarization with laboratory equipment, Ohm’s law and Thevenin equivalence.

2. Voltage Dividers: Test the voltage divider rule, experiment with potentiometers, and assemble and test the mic pre’s “Pad” section.

3. Kirchhoff’s Law and Wheatstone Bridge: Signal transmission, Balanced Lines.

4. Capacitors and RC Filters: Capacitor behaviour, capacitive reactance and filtering. Assemble and test the HPF and RF filter of the mic pre to learn about simple high-pass and low-pass filters.

5. Transformers and Inductors: transformer voltage step-up, step down and frequency response. Reflected impedance.

6. Diodes and Rectifiers: Power supply rectifiers and diode protection to demonstrate forward voltage drop and diode action. Teaches AC to DC conversion and power supplies.

7. Transistors and Amplifiers: The transistor amplifier module teaches the basics of BJT operation and the fundamentals of common emitter and emitter follower amplifiers. The two-transistor shunt feedback class-A amplifier used in the “Baby Pre” combines both these implementations

8. Operational Amplifiers and Comparators: The output section of the EMP uses the basic behaviour of inverting and non-inverting op amp configurations in order to produce a balanced output.

9. Dynamic Range, CMR, and Data Sheets : Measure the gain range, equivalent input noise, common-mode rejection, input impedance, output impedance, and frequency response. Generate data sheet in the same format commonly provided by microphone preamplifier manufacturers.